Embodiments of the subject matter disclosed herein generally relate to turbo machines and more particularly, to managing a pressurized process fluid between a shroud and an impeller of a turbo machine.
During the past years, with the increase in price of fossil fuels, the interest in many aspects related to the processing of fossil fuels has increased. During processing of fossil fuels, fluids are transported from on-shore or offshore locations to processing plants for subsequent use. In other applications, fluids may be transported more locally, for example, between sub-systems of a hydrocarbon processing plant to facilitate distribution to end-users.
At least some fluid transport stations use turbo machines, such as compressors, fans and/or pumps that are driven by gas turbines. Some of these turbines drive the associated fluid transport apparatus via a gearbox that either increases or decreases a gas turbine output drive shaft speed to a predetermined apparatus drive shaft speed. In other rotary machines, electrically-powered drive motors, or electric drives are used in place of mechanical drives or in conjunction with mechanical drives (i.e., gas turbines) to operate the rotary machine.
Regardless of the particular setting, i.e. on-shore, off-shore, subsea, etc. and regardless of whether the turbo machine is turbine or motor driven, there is an ever present need to increase the efficiency, decrease the costs, and reduce the environmental impact of fossil fuel processing, and in particular, of rotary machines involved in such processing.
As a result of this ever present need, the performance of rotary machines continues to improve. Today's rotary machines are not only faster, more efficient, and environmentally friendly; they are capable of processing more corrosive substance at higher temperatures and higher pressures than ever before.
While these improvements are welcome, existing solutions for controlling these processes are oftentimes inadequate to meet the demands of working in the harsh environments brought about by such improvements.
One area of particular concern is seals. Brush seals are typically provided between the rotor and a stator of a turbo machine to maintain a pressure differential between an upstream and downstream side of the brush seal. Brush seals are vulnerable to diminished performance and potential damage when process fluid bears against the seal with excessive rotational velocity components, oftentimes referred to as excessive process fluid swirl. In the past, process fluid swirl between the rotor and the stator has been addressed through the introduction of so called swirl reducers or swirl brakes positioned upstream of the brush seal. These components typically include circumferential components having axial passages which reduce the swirl in the process fluid traveling through. With increased speed of the rotor, the rotational speed of process fluid swirl also increases. Forcing high speed fluids through such components may contribute to a reduction in the efficiency and/or the performance of the turbo machine.
What is needed is a turbo machine capable of providing improved sealing, reduced process fluid swirl, more uniform speed distribution of the process gas, and improved turbo machine performance.